Insulator



Sept. 30, 1930.

G. A. BURNHAM 1,777,0714

INSULATOR Filed April 14, 1926 Patented Sept. 30, 1930 UNITED sTATEsPATENT OFFICE GEORGE A. BURNHAM, F SAUGUS, MASSACHUSETTS, ASSIGNOR TOCONDIT ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON,MASSACHUSETTS, A'CORPOBA- TION OF MASSACHUSETTS INSULATOB `Applicationled April. 14, 1926. Serial N0. 102,069.

This invention relates to electric insulators, as insulating bushings,especially adapted, although not necessarily limited for use in hightension switches.

The terminals of an electric switch must have sufficient spacing toprevent lash-overs between them, and where air is the insulating medium,the terminals must necessarily be spaced widely apart to providesuicient insulation', if high voltages are employed. To provide therequisite spacing with vertically disposed insulating bushings wouldnecessitate switch casings of Va prohibitive size; so it has been commonpractice to obtain the desired spacing at the terminal and of thebushing by inclining the bushings outwardly. This construction, whileproviding an increased spacing at the top of the insulator, mustnecessarily decrease the spacing at the lower end of the insulator. Toacertain extent this may be permissible since the lower exposed terminalsof the insulator are immersed in oil; but it is evident that if thebushings are inclined to any great extent,

the lateral dimensions of the switch casing must be increased tomaintain a safe spacing of the lower terminals.

Consequently an objectof this invention is the provision of an insulatorso arranged that, when two or more of them are used in an electricswitch or other similar apparatus, a suitable close spacing is providedbetween them at the lower ends thereof under the oil while a suitablewide space is provided between them at their upper and air-exposed ends.

A further object of this invention is generally to improve theconstruction of electric insulators.

Briefly the insulator embodying my invention comprises twoangularly-related insulator-sections connected rigidly together, with aconductor extended therein which is composed of two angularly-inclinedsections which correspond with and lie within said singularly-relatedinsulator sections.

Certainfeatures of this invention are described and claimed in myco-pending application Serial No. 102,071 filed April 14,

1926. The broad idea of a flexible insulated cable within an enclosingcasing', at least a part of which is insulating, is described andclaimed in my copending application Serial No. 729,625, led August 1,1924. 7

Fig. 1 is a sectional elevationthrough an insulator embodying theinvention.

Fig. 2 is a sectional elevation through an electric switch havinginsulators with which this invention is particularly concerned.

Fig. 3 is a modification of the insulator of Fig. 1;

The insulator embodying the invention is of the bushing-type andcomprises the straight upper tubular insulator body or shell 10 and thestraightv lower tubular insulator-body or shell 12. Said upper shell isadapted to be exposed to the atmosphere and is provided with a pluralityof petticoats 14 as is usual practice. Said lower shell is adapted to beimmersed in oil or other insulating or arcquenching iluid and may beprovided with a plurality of corrugations 16, as is usual practice. Bothshells are provided with conductor-passages 18 therethrough and both mayhave attaching flanges 22 and 23 cementedv to their lower and upperends, respectively. Said upper and lower shells are secured to theopposite ends of a tubular metal connecting member or tube 20 and theflanges of said insulating bodies are attached by bolts 24 to flanges 26and 28 provided at the opposite ends respectively of said tube. Inaccordance with the invention said tube is suitably bent intermediateits ends to follow a regular curve and to provide angularly-relatedupper and lower sections so that said insulating shells are angularlyinclined with respect to each other.

The conductor-structure for the insulator preferably comprises a section30 of commercial high-tension` electric cable as set forth in myco-pending application Serial No. 729,625, filed .August 1, 1924. Saidcable comprises a central conductor 32, which preferably is stranded, abody of insulating material 34, as superimposed layers of paper, on theconductor, and a lead protective sheath 36 enclosing the insulatingmaterial. The cable-section is of suitable length and diameter to enterthe insulator-structure and is bent to conform with the shape of theinsulator and to lit snugly therein. The lead sheath is removed from theends of the cablesection, as indicated, leaving a section of the sheathat the middle of the cable and exposing the insulation at the ends. Someof theexposed insul tion is removed to pro- V vide surfaces which taperfrom the lead sheath to the exposed ends of the conductor, as indicatedat 34. rihe conductor-structure thus formed is received within theinsulatorstructure in the manner illustrated in l. The'lead sheath isreceived within the bent connector tube 2O and is approximately'co-eiitensive therewith and may be grounded thereto in any suitablemanner not necessarily shown. rEhe tapered end-portions are receivedwithin the insulator shells 10 and l2. The exposed ends of thecable-conductor may be connected with suitable terminalmembers carriedby the ends of the insulator-bodies l0V and l2. As here shown, a lug 38is received the lower open end of the insulator-body 12 and has a recesstherein in which the exposed lower end of said conductor is received andsoldered. Said lug has a reduced and enteriorly screw-threaded extension42 which extends loosely through a metal ferruleor capcemented to thelower end of said insulator-body.v A suitable terminal-member ehi, herevshown as a Contact bloclr for an electric switch, is screw-threaded onsaid extension 42. Lock-nuts 46 serve to loch said Contact block inplace and said lug to said cap 4:0. ri`he upper end of the insulator maybe arranged in a similar manner except that the lock-nuts 46 arepreferably arranged to clamp va. circuit-lead between them.

. lf desired, the insulator may be filled with an insulating medium, asoil or a compound, through. the filler-plug 48 which is screwthreaded inthe metal shell 20. Y

The upper flange 26 of said shell is extended outwardly beyond theflange 22 and is adapted to be secured to a support 60, as a switchcasing, by suitable bolts 50.

7Eig. 2 illustrates the application of a pair of the insulators abovedescribed to the casing of a high-tension electric switch having' aswitch frame which is secured to and comprises a cover for the oilreceptacle 62. rlhe top wall of said casing is formed with apertures `64through which a pair of insulators are passed and are fixed to thecasing by bolts 50. Said insulators are so arranged Y in the switchcasing that the upper portions thereof are inclined upwardly andoutwardly, whereby to separate the exposed upper terminals widelythereby to prevent flash- Aovers therebetween. The lower portions ofsaid .insulators are relatively closely spaced and are parallel andvertical. The oil level a-a in the casing is adapted to be above thelower end of the metal shell 20, or at least above the lower end of theinsulator-flange 23, which is at casing or ground potential. i movableswitch member 65 cooperates with the contact blocks lll carried by thelower ends of said insulators and the operating mechanism 65a for saidmovable switch member is contained in a mechanism-well 66 which isdisposed between said insulators and between the divergent portionsthereof.

ils thus arranged the lower ends of the insulators may be as closelyspaced as is desirable, with the upper ends of the insulators widelyspaced, and yet the casing dimensions may be made smaller than ispracticable with the usual straight and inclined insulators, therebyresulting in a compact and economical structure.

For some purposes, l may replace the cablesection of the insulator witha bare bent rod 68, see Fig. 3, which rod is extended through the endsof the insulator and is connected with the terminals thereon, and liesapproximately axially within the insulator and free from the side wallsthereof. The insulator is adapted to be filled with an insulatingmedium, whereby to insulate the rod from the metal shell 20. Aninsulating spacer-member 70 may be disposed on said rod, at the bentportion thereof, and engage with. said metal shell, whereby to cooperatewith the ends of the insulator in holding said rod in position. Saidspacer-member 70. may have passages 7 2 therethrough, through which theinsulating medium may pass.

The construction may be otherwise modified without departing from thespirit of the invention.

I claim.:

l. A bushing-type electric insulator having angularly related sections,a terminal connector carried at the end of each of said sections, and acorrespondingly-shaped continuous conductor contained in said insulatorand connected with said terminal connectors and a similar insulatorhaving Va section thereof in divergent relationship with the similarsection of said first mentioned insulator.v

2.V A bushing-type electric insulator having angularly-related sections,each section having an end terminal connector, a correspondingly-shapedrconductor contained therein and connected with said terminal connectors,and an attaching member intermediate the ends of said insulator and asimilar insulator having a section thereof in divergent relationshipwith the similar section of said iirst mentioned insulator.

8. A. bushing-type electric insulator having a bent shell, straightinsulator bodies carried by the opposite ends of said shell, and a bentconductor disposed within said shell and insulator-bodies, and a similarinsulator having a section thereof in divergent relationl G il llt! shipwith the similar section of said first mentioned insulator.

4. A bushing-type electric insulator having a bent metal shell, straightinsulator bodies carried by the opposite ends of said shell, a bentconductor disposed within said shell and insulator-bodies, and anattaching member carried by said metal shell, and a similar insulatorhaving a section thereof in divergent relationship with the similarsection of said first mentioned insulator.

5. A bushing-type electric insulator `comprising a tubularconnecting-member having relatively-inclined end-sections, .and straight3 insulator-bodies carried by said inclined endsections, and a similarinsulator having a section thereof in divergent relationship with thesimilar section of said first mentioned insulator.

6.7A bushing-type electric insulator comprising a tubularconnecting-member having relatively-inclined end-sections, and straightinsulator-bodies carried by said end-sections and having passagestherein aligned with the passage in said connectingmember, and a similarinsulator having a section thereof in divergent relationship with thesimilar section of said first mentioned insulator.

7. A bushing-type electric insulator cornprising a tubularconnecting-member having relatively-inclined end-sections, straightinsulator-bodies carried by said inclined end-sections and a conductorextended through said insulator-bodies and connecting member andinsulated from said connecting-member, and a similar insulator having asection thereof in divergent relationship with the similar section ofsaid first f mentioned insulator.

8. A bushing-type electric insulator coming shells carried by the endsof said tube, a bent conductor extended through said tube and shells,and means engaging said conductor Within said tube arranged to hold itfrom contact with said shell, and a similar insulator having a sectionthereof in divergent relationship with the similar section of said firstmentioned insulator.

9. A bushing-type electric insulator comprising a bent tube, straightinsulating shells carried by the ends of said tube, a bent conductorextended through said tube and shells, and an insulating mediumsurrounding said conductor, and a similar insulator having a sectionthereof in divergent relationship with the similar section of said firstmentioned insulator.

10. A bushing-type electric insulator comprising akbent metaltube,straight insulating shells carriedby the ends of said tube, a bentconductor-structure contained within said tube and shells comprising aconductor extended through said tube and shells,

ductor and extended through said tube and shells and having taperedend-portions disposed Within said shells, and a metal sheath carried bysaid insulating body and contained mainly Within saidtube.

12. A bushing-type electric insulatorcom- `prising a bent metal tube,straight insulating shells carried by the ends of said tube, and a bentconductor-structure contained Within said tube and shells comprising abent conductor extended through said tube and shell, and a bent body ofinsulation carried by said bent conductor, and a similar insulatorhaving a section thereof in divergent relationship with the similarsection of said first mentioned insulator.

13. An oil-filled bushing-type electric insulator comprising acontinuous tubular structure having insulating end-portions which areinclined out of a straight line, terminal connectors disposed at theends of said insulator and arranged to provide an oil-tight closurethereat, and an attaching member intermediate its ends, and a similarinsulator having a section thereof in divergent relationship With thesimilar section of said first mentioned insulator.

14. A bushing-type electric insulator comprising a bent metal` tubehaving outstanding flanges at its opposite ends, straight insulatorshells disposed on the opposite ends of said tube, said shells havingflanges fixed thereto, and means securing said flanges to saidtube-flanges, one of said tube-flanges outstanding beyond itscooperating shellflange for attachment to a support, and a similarinsulator having a section thereof in divergent relationship With thesimilar section of said first mentioned insulator.

In testimony whereof, I have signed my name to this specification.

GEORGE A. BURNHAM.

